95 Wrangler 2.5L overheated badly (long)
 

A 95 Wrangler with the 2.5L was brought to me for repair after it was badly
overheated.

I noted these things during disassembly/diagnosis:
-radiator leaking badly
-coolant in cylinders 1,2,&3
-#2 head bolt loose
-looks like valve cover was off before, maybe the head too

I sent the head to the machine shop for crack detection, and resurfacing.
(I should have asked to have the valves/seats checked also but we'll get to
that in a bit)

Head came back with no cracks, but it had to be milled .014" to get it true.
Machine shop says this is in spec. Ok, sound like alot, especially for
something with a non adjustable valvetrain.

I reassembled everything and started the engine. It runs horrible. I pull
the plugs, and #2 isn't running. Compression test shows #1 - 90psi, #2 -
25psi, #3 - 125psi, #4 - 150psi. Leak down test shows all four intake
valves leaking badly. I loosen the rocker arms and the leaks decrease a
little.

Head comes back off and I find that the intake valves are badly warped. I
can see light. Lightly lapping the valves reveals the high spots.

On top of all that, the fresh oil I just put in looks funny. There are
pools of it in the rockers and it looks badly aerated or like its mixed with
something. The cooling system was filled with straight water and no
thermostat or radiator cap. The engine ran several times for a total of
approx 6 mins.

The head will be sent to the machine shop to repair the leaking valves.

Questions:
- Are there valve train shims available? ( it seems like the head has been
cut too far and the valves are being held open)

- what is going on with the oil? What can I do to diagnose this?


Regards,
Brent

I read a lot of repair manuals and tolerances for milling a head is
0.08. Sounds to me like they did mill too much. When you do get the
head back check it for wrapage. Do you have a repair manual on this
vehcile? I would check the specs on to see the maxium of how much the
head should be milled. Also you may be able to call a dealership or
check the internet for this info. Somewhere it sounds like water is
getting mixed in with the oil. The intake manifold could have a crack
in it. It might need to be crack detected also and checked for
wrapage. I don't know about the shims.

> The head will be sent to the machine shop to repair the leaking valves.
>
> Questions:
> - Are there valve train shims available? ( it seems like the head has been
> cut too far and the valves are being held open)
>
> - what is going on with the oil? What can I do to diagnose this?

Here are just some 'maybe's, Brent
- (1) Speaking generically...
Any time you true the heads by machining, or you machine the valve seats or
valves, you
change clearances a bit. But this is normally not critical, especially on
lower compression engines,
and is usually compensated by the valve adjustment process.

This engine was apparently an adaptation of one of the older AMC straight 6
designs. On the old ones I know about, the valves were adjustable (even
hydraulics require some adjustment). Are these valves adjustable, or are
they the 'tighten down' type?

If those valves are not sealing properly due to adjustment, warping, wear,
etc, it can run horribly.
Once you get the head back with sharp valves, maybe this will go away.

-(2) The oil problem could be a number of things..
Maybe the head wasn't cracked, but perhaps some part of the block IS
Maybe, even though you changed the oil and filter, you didnt get all
the water out and it is
showing up now.
Maybe you got the head gasket on upside down...on some engines it is
easy to do, and
not all of them are very forgiving

I suggest you also look into the valvetrain to see if there are deeper
problems, such as jumped time, flattened cam lobes, bad lifters, etc. And
there are the relatively simpler issues such as
spark plug wires bad or on the wrong plugs, and distributors that are off a
tooth or ten.

A long time ago, AMC used the Pontiac 2.5 litre Iron Duke in some of their
cars. I dont
think this would have been one of them though.

The Iron Duke had lace panties...many of them cracked through into the water
jacket
just above the lifters.

Just mentioned this in case there might be a connection.